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53 lines
2.1 KiB
C++
53 lines
2.1 KiB
C++
#pragma once
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#include <type_traits>
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#include <boost/iterator/transform_iterator.hpp>
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namespace collections
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{
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/// \brief Strip type off top level reference and cv-qualifiers thus allowing storage in containers
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template <typename T>
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using unqualified_t = std::remove_cv_t<std::remove_reference_t<T>>;
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/** \brief Returns collection of the same container-type as the input collection,
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* with each element transformed by the application of `mapper`.
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*/
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template <template <typename...> class Collection, typename... Params, typename Mapper>
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auto map(const Collection<Params...> & collection, Mapper && mapper)
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{
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using value_type = unqualified_t<decltype(mapper(*std::begin(collection)))>;
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return Collection<value_type>(
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boost::make_transform_iterator(std::begin(collection), std::forward<Mapper>(mapper)),
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boost::make_transform_iterator(std::end(collection), std::forward<Mapper>(mapper)));
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}
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/** \brief Returns collection of specified container-type,
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* with each element transformed by the application of `mapper`.
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* Allows conversion between different container-types, e.g. std::vector to std::list
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*/
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template <template <typename...> class ResultCollection, typename Collection, typename Mapper>
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auto map(const Collection & collection, Mapper && mapper)
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{
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using value_type = unqualified_t<decltype(mapper(*std::begin(collection)))>;
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return ResultCollection<value_type>(
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boost::make_transform_iterator(std::begin(collection), std::forward<Mapper>(mapper)),
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boost::make_transform_iterator(std::end(collection), std::forward<Mapper>(mapper)));
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}
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/** \brief Returns collection of specified type,
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* with each element transformed by the application of `mapper`.
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* Allows leveraging implicit conversion between the result of applying `mapper` and R::value_type.
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*/
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template <typename ResultCollection, typename Collection, typename Mapper>
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auto map(const Collection & collection, Mapper && mapper)
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{
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return ResultCollection(
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boost::make_transform_iterator(std::begin(collection), std::forward<Mapper>(mapper)),
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boost::make_transform_iterator(std::end(collection), std::forward<Mapper>(mapper)));
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}
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}
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